A synthetic pulmonary surfactant composition for use in the treatment of inflammatory or cell proliferation disorders of the lungs is provided. The composition comprises a lipidaceous carrier and a peptide complex of poly-L-lysine or a pharmaceutically acceptable salt thereof and poly-L-glutamic acid or poly-L-aspartic acid or a pharmaceutically acceptable salt thereof, the peptide complex having a charge-neutralised region and a positively-charged region. The synthetic pulmonary surfactant composition may be provided in an inhalable formulation. The synthetic pulmonary surfactant composition may also be combined with a drug for use in treating a lung infection, particularly a lung infection characterised by inflammation in the lungs so that the combination provides dual immunomodulatory effects.
